Generally, in image display devices such as liquid crystal displays (LCD) or organic light emitting diodes, polarizers are disposed on both sides or one side of a panel substrate in order to provide an image that is bright and has favorable color reproducibility. A polarizer is generally prepared by dyeing a polyvinyl alcohol-based polymer film with iodine or dichroic dye, then crosslinking the result using a crosslinking agent, and orienting the result using a method such as elongation.
Meanwhile, recent display devices tend to be slimmer, and a thickness of a bezel unit, in which a screen is not displayed, and an edge thickness tend to be minimized in order to obtain a large screen. In addition, components such as a camera tend to be installed in a display device in order to exhibit various functions, and attempts to bleach or provide various colors in a product logo or an edge area have been tried considering design factors.
However, in an existing polarizing plate, the whole area of the polarizing plate is dyed with iodine and/or dichroic dye, therefore, the polarizing plate exhibits a dark black color, and as a result, various colors are difficult to be provided in an area of display devices, and particularly, when a polarizing plate is located on components such as a camera, the polarizing plate absorbs 50% or greater of the quantity of light causing a problem such as visibility decline in a camera lens.
In order to solve such a problem, a method of physically removing a polarizing plate in a site covering a camera lens by punching a hole (bore) on a portion of the polarizing plate using a method such as punching and cutting has been commercialized.
However, such a physical method degrades the appearance of an image display device, and may damage a polarizing plate due to the nature of a hole-punching process. Meanwhile, a punching site of the polarizing plate needs to be formed in an area sufficiently away from an edge in order to prevent damage such as the tearing of the polarizing plate, and as a result, a bezel unit of the image display device becomes relatively wide when such a polarizing plate is used, which leads to a problem of being out of a recent narrow bezel design trend in an image display device. In addition, when a camera module is installed on a punching unit of a polarizing plate such as above, a camera lens is exposed to the outside causing a problem of camera lens contamination and damage when used for a long period of time.
Accordingly, a method of bleaching a local area of a polarizer needs to be provided in order to solve the problems described above by forming a depolarized area of a polarizing plate without punching, and at the same time, a polarizer having high heat resistance needs to be manufactured so that transmittance does not decrease even when the depolarized area is left unattended for a long period of time under a high temperature.